Heretofore, an emulsification and aggregation method is known as one example of toner production. The emulsification and aggregation method is for producing toner particles having a desired size by aggregating extremely fine resin particles in a solution (build-up production method), and this is excellent in that the toner particle size distribution can be sharp. Another advantage of the emulsification and aggregation method is that, since the resin viscosity of the aggregated resin particles can be controlled by utilizing the surface tension thereof, the form of the toner particles can be continuously controlled to any form of from an amorphous form to a spherical form (JP-A 8-179553).
For controlling the viscosity of the resin to be used as a toner binder herein, there are a method of utilizing heat and a method of using a solvent.
However, in the method of controlling the resin viscosity by utilizing the heat generated by heating the resin, the resin must be heated at a temperature not lower than the glass transition temperature (Tg) thereof when the resin particles are aggregated into spherical toner particles. Therefore, when a resin having a high melt viscosity is used, then it must be heated at an extremely high temperature, and in such a case, a specific apparatus such as a pressure apparatus is needed when the heating temperature therein is higher than the boiling point of water. This results in the increase in the production costs of the toner.
In the method of controlling the resin viscosity by using a resin, a diluted solvent must be added to the system and therefore a large-size reactor is needed, which, therefore reduces the toner production efficiency. When a solvent not diluted sufficiently is added, then the resin particles may mutually aggregate together and, after all, the form of the toner particles could not be controlled.